This project is designed to increase basic knowledge of how people spontaneously form impressions of other people, of the effects of this implicit knowledge on judging others, and of the conditions under which people can control their implicit knowledge's effects. Impressions of others are fundamental determinants of social relations. They can promote mental health or mental illness, and affect people's receipt of medical care. They affect people's effectiveness in work groups, friendships and social support networks, choice of reference groups, inter-group cooperation and conflict, and more. Most research on how people form and use impressions focuses on intentionally formed, explicit impressions, measured through self-reports. But recent research shows that much knowledge of others is implicit and not available to self-report. This implicit knowledge can affect explicit judgments of others without the judges' awareness. How much control can people have over their implicit impressions' effects, once they are made aware of them? What affects the degree of control they have? This project proposes ten experiments designed to provide some precise, initial answers to these questions. They examine effects on control of time delays between forming implicit impressions and trying to control their effects; of doing other cognitive tasks, both when implicit impressions are formed and when control is attempted later; of having various goals when implicit impressions are initially formed; and of forewarning and suspicion. They investigate whether implicit impressions of people differ from implicit impressions of inanimate objects, and factors that may affect controlling implicit stereotypes. These studies open up new areas of research, and demonstrate new methods to pursue them. They should contribute to better understanding of any health problems where implicit impressions of others are part of the problem, or could contribute to the solution.